This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The overall goal of my research is to identify mechanisms responsible for sperm differentiation using mice to understand normal development and aid in the treatment of human male infertility. Mice with the repro27 chemically-induced mutation display male-specific infertility characterized by cell dealth in late meiosis and abnormal differentiatiion leading to abnormal sperm heads and tails. repro27 mice have a point mutation in the golgin subfamily A member 3 (Golga3) gene that inserts a premature stop codon in exon 18. Protein expression analysis using Western blotting suggests that GOLGA3 protein is degraded in mutant mice. GOLGA3 is a Golgi complex protein implicated in protein trafficking of certain proteins, apoptosis, and spermatogenesis. GOLGA3 is expressed in both somatic Sertoli cells and germ cells but its function is not known. The objective of this proposal is to understand GOLGA3's role in spermatogenesis by utilizing repro27 mutant mice known to carry a mutation in this gene. The central hypothesis is that repro27 mutant mice exhibit multiple spermatogenesis defects resulting from disrupted GOLGA3-dependent pathways. Although Golga3 mutations have not been identified in humans, identification of affected genes and pathways may be conserved. Thus, repro27 mice will be used to 1) conduct spermatogonial stem cell transplant experiments to determine if GOLGA3 function is germ cell specific;and 2) study the role of GOLGA3 in the testis at transcriptional and post-translational levels. Spermatogenesis in reciprocal stem cell transplant experiments will be used to determine cell type requirements. Validated protein targets and demonstrated protein interactions will dissect GOLGA3 pathways. Results will facilitate our understanding of spermatogenesis and may provide new clues and treatment options for human male infertility.